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mmaelzer/image-poll.js

Created June 24, 2015 04:35
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image polling
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image-poll.js
/** =========================== SERVER =================================== */
var express = require('express');
var MjpegCamera = require('mjpeg-camera');
var app = express();
// Create an MjpegCamera instance
var camera = new MjpegCamera({
name: 'backdoor',
url: 'http://192.168.7.1/video'
});
// Start streaming
camera.start();
app.get('/frame', function(req, res) {
res.set('Content-Type', 'image/jpeg');
res.status(200).send(camera.frame);
});
app.listen(3000);
/** =========================== BROWSER =================================== */
function startImageFeed(imageUrl, id) {
var img = document.getElementById(id);
var stop = false;
(function setSrc() {
if (stop) return;
img.src = imageUrl;
})();
img.onload = setSrc;
img.onerror = setSrc;
return function() {
stop = true;
};
};
var stop = startImageFeed('/frame', 'video-image');
// Stop "video" feed after 30 seconds
setTimeout(stop, 30000);
@baur
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baur commented Dec 4, 2020

Hi, Friend!
How it can be scale for many cameras app.get ('/ frame / CameraID')
Start stream only when requested and stop after N minutes

@mmaelzer
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mmaelzer commented Dec 5, 2020

This code is untested, but the approach should work.

class Streamer {

  constructor(cameraOptions, opt_stopAfterMinutes) {
    this.camera = new MjpegCamera(cameraOptions);

    this.stopAfter = (opt_stopAfterMinutes || 5) * 60 * 1000; // hold in ms
    this.timeout = null;
  }

  getFrame() {
    clearTimeout(this.timeout);
    return new Promise((resolve, reject) => {
      if (this.camera.connection) {
        resolve(this.camera.frame);
      } else {
        this.camera.start()
        this.camera.once('data', (frame) => { resolve(frame); });
        this.camera.once('error', (err) => { reject(err); });
      }
      this.timeout = setTimeout(() => { this.camera.stop(); }, this.stopAfter);
    });
  }

}

const streamer = new Streamer(cameraOptions, 5 /** Stop after 5 minutes of streaming if no new requests come in */);
app.get('/frame', function(req, res) {
  streamer.getFrame()
    .then(frame => {
      res.set('Content-Type', 'image/jpeg');
      res.status(200).send(frame);
    })
    .catch(err => {
      res.set('Content-Type', 'text/plain');
      res.status(500).send(err.toString());
    });
});

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